The donor contributes healthy mitochondrial DNA (mtDNA) to replace defective mtDNA responsible for a host of serious inherited diseases. Housed in the mitochondria – the cell's "power plants" – and not the cell nucleus, mtDNA accounts for only 0.1% of a person's genetic make-up.

Mitochondrial diseases are rare, affecting around one in 5,000 of the population, but can be devastating for families. They cause a wide range of different conditions affecting muscles, nerves and organs, and can lead to blindness, deafness, autism and learning difficulties.

One of the regulations laid before parliament says that the donor would not be classed as a parent related to the child. Others say that the fertility regulator must assess each case for a significant risk of disability or serious illness, and that fertility clinics would need to obtain a special licence to offer the treatment.

In addition, any child born as a result of the technique would have no automatic right to information about the donor.

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These guidelines make sense. There's no point in making the donor — who contributes a painfully minuscule amount of DNA to the child — an officially recognized related parent.

An affirmative vote by the U.K. parliament could encourage other countries, like the United States, who are also considering the procedure.